1. Field of the Invention
The invention concerns a rotating envelope x-ray radiator.
2. Description of the Prior Art
A rotating envelope radiator is described in DE 196 12 698 C1. A cathode and an anode are permanently mounted inside a vacuum-sealed radiator housing (envelope). The tube is mounted such that it can rotate. An electron beam directed from the cathode to the anode is deflected by a magnetic deflection device that is stationary relative to the tube so that the beam is held stationary in the deflected position. The radiator housing is provided with a cooling device for dissipation of the heat formed by the deceleration of the electron beam in the anode. For example, the cooling device can be an external housing surrounding the radiator housing. For dissipation of the heat a coolant (for example insulating oil) circulates by means of a pump in an intervening space formed between the external housing and the radiator housing.
Furthermore, from DE 103 19 735 A1 a rotating envelope radiator is known that has a radiator housing that is surrounded by an external housing. The radiator housing is mounted by bearings that are arranged in the housing, such that the radiator housing can rotate around an axis. The radiator housing thus rotates in the stationary housing. A coolant is supplied and led away in an intervening space formed between the external housing and the radiator housing, with the coolant circulating around the outside of the radiator housing. In order to counteract the formation of transverse eddies in the coolant, recesses are arranged on an outside surface of the radiator housing that is located in contact with the coolant. The recesses are groove-shaped on the outside surface and proceed in the circumferential direction of the radiator housing. The recesses are concentrically arranged on the facing surfaces.
Further rotating envelope radiators are known from DE 199 29 655 A1 and the corresponding U.S. Pat. No. 6,426,998 as well as from DE 103 35 664 B3 and from DE 10 2004 003 370 A1.
In practice, in operation at high rotational frequencies of the tube of more than 200 revolutions/minute, a significant increase of the power of the pump for circulation of the coolant is required to maintain sufficient cooling. Given an increase of the power of the pump it is also observed that the transport of the coolant sometimes significantly slows or even completely comes to a standstill in a region of the anode that is highly thermally loaded. An unwanted severe heating of the anode can occur as a result.